Engine backfires under full throttle

[Monte666]

Had my car inspected last week found my valve covers loose when I got it back and now it's backfires under full throttle but only in gear any opinions or help would be appreciated I know there are alot of smart people on here

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[Ms Grumpy]

I would take it back to the place that inspected it, did they do anything to it?

[shadowgray396]

Did the vacuum lines get hooked back up or do you have a cracked one?. Almost sounds like the distributor is not advancing correctly when under a load.

[Monte666]

I took it back to my normal shop this morning they think big o changed my timing crossing my fingers

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[Monte666]

They changed my plugs at big-o could it be that they are gapped wrong

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[Hank70SS]

Unless the gap is WAY off it shouldn't cause a backfire. Idle's smooth I assume? As Ray said, maybe timing or vacuum lines or timing.

[Monte666]

I did just change carburetors from a old holley to a new performer ill check my lines

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[Monte666]

It was my points timing running great now Thankyou everyone this place is grwst

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[Ms Grumpy]

Glad to hear.

[Monte666]

Found some weird pitting on #6 cylinder seal on the intake manifold was sucking quite a bit of air got a new performer to replace it

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